Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Semiconductor devices perform a wide range of functions such as analog and digital signal processing, sensors, transmitting and receiving electromagnetic signals, controlling electronic devices, power management, and audio/video signal processing. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, diodes, rectifiers, thyristors, and power metal-oxide-semiconductor field-effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, application specific integrated circuits (ASIC), standard logic, amplifiers, clock management, memory, interface circuits, and various signal processing circuits.
An image sensor is a type of semiconductor device that detects and records an image by converting the variable attenuation of light waves or electromagnetic radiation into electric signals. Image sensors convey information related to an image by communicating signals in response to incident electromagnetic radiation. An image sensor may include an array of imaging pixels. The imaging pixels include photosensitive elements, such as photodiodes, that convert the incoming image light into image signals. A typical image sensor can have hundreds of thousands or millions of pixels. Image sensors use control circuitry to operate the imaging pixels and readout circuitry for reading out image signals corresponding to the electric charge generated by the photosensitive elements.
An image sensor can be implemented with semiconductor charge-coupled devices (CCD) and active pixel sensors in complementary metal-oxide-semiconductor (CMOS) or N-type metal-oxide-semiconductor (NMOS) technologies with applications in electronic devices, such as digital cameras, computers, cellular telephones, video recorders, medical imaging equipment, night vision equipment, thermal imaging devices, radar, sonar, and other image detecting devices that gather incoming image light to capture an image.
In an imaging sensor, each pixel typically includes a photosensitive element such as a photodiode that receives incident photons (light) and converts the photons into electrical signals. The imaging system contains an image sensor die with an image sensor integrated circuit and an array of photodiodes formed in a semiconductor substrate. Alternatively, the imaging system contains an image sensor die having an array of photodiodes formed in a semiconductor substrate and the image sensor die is mounted on a digital signal processor (DSP) die.
A glass layer may be placed over the image sensor for protection. A redistribution layer (RDL) may be formed over a surface of the semiconductor die opposite the glass layer for electrical interconnect. The single RDL limits the interconnect capability of the semiconductor die containing the image sensor.